The present invention is concerned with the materials and methods for constructing a new type of lipid vesicle, called a "liposoil". Liposoils are micron-sized vesicles containing oil, dried egg, surfactant and a diluent. The diluent can vary in salinity from water suitable for injection to solutions with the salinity of seawater. Liposoils are produced using high shear force without the use of organic solvents and are freely suspendable in water. The diluent or water content of these structures is low, normally 20-40% on a volume per volume basis. Since all materials utilized in the construction of liposoils are food grade, USP or NF grade materials, liposoils are suitable for human and animal enteral use applications. Liposoils are stable at temperatures from 4.degree. to 37.degree. C. and are not degraded by exposure to strong acids and base. Due to the ability to use high salinity diluents in formation of these structures these materials have potential marine applications, particularly as a marine food. The size and the fact that they are constructed of edible materials allows filtration and metabolism of these structures by marine filter feeders. The liposoils have a high protein content from the dried egg used in their formation, which is also adventageous in their use aqs a marine food.
Liposoils differ from classic liposomes in several ways. Classic liposomes were constructed of phospholipids such as phosphatidylcholine or lecithin extracted from a variety of sources (including eggs) but dried whole egg or egg yolk was not used as a wall material. Both egg yolk and whole egg have a high protein content in addition to the lipid content. Classic liposomes do not have this high protein content, and, in fact, the protein which can be encapsulated may be limited. This limitation is not found in liposoils. In addition, only small amounts of oil, compared to large amounts of oil used in liposoils, could be incorporated before the liposome broke down. Still another difference between the classic liposomes and the liposoils is the ability to use high saline solutions in the manufacture of liposoils. High saline solutions prevented the formation of the classic liposomes.
The method of manufacturing liposoils is also different than that used in classical liposome formation. Classical liposomes are normally formed utilizing the Bangham method, or a variant thereof. In the Bangham method, the lipids are dissolved in organic solvent, the solvent is removed to form a film, and the film is rehydrated with an aqueous solution to form liposomes. Organic solvents are not needed to make liposoils and, in fact, may impede the formation process.
Although some workers in the lipid vesicle field have used procedures other than Bangham method, and materials other than classic phospholipids, there is little work on vesicles made using both phospholipids and surfactants in the vesicle walls. For example, although U.S. Pat. No. 5,234,767, entitled "Hybrid Paucilamellar Lipid Vesicles", the disclosure of which is incorporated herein by reference, discusses vesicles which may have a phospholipid and nonphospholipid in the vesicle wall, the phospholipids discussed are purified phosphatidylcholine and the like, not crude dried egg yolk or dried egg. These materials do not have the high protein content of the liposoils of the present invention. In addition, there is no discussion in this patent of using high salinity diluents nor that less water could be used than lipid.
The ability of the liposoils to have high oil content and be made using high salinity diluents such as sea water leads to an optimum usage in the marine environment, particularly in the marine food environment. Little or no work has been done in this field using liposomes because of the stability problems in this high salinity environment. The liposoils of the present invention are much better suited to this environment than classic liposomes or even most lipid vesicles using nonphospholipid materials. In addition, most nonphospholipid materials used to make lipid vesicles are not food grade or safe for incorporation into the food chain.
Accordingly, an object of the invention is to provide a new type of lipid vesicle, the liposoil, which has high oil content, utilizes dried egg or egg yolk, and can be made in a high salinity environment.
A further object of the invention is to provide a method of making the liposoils of the invention.
A still further object of the invention is to provide a marine food and/or pharmaceutical which is useful in a high salinity environment.
These and other objects and features of the invention will be apparent from the following description and the claims.